Systems and methods for battery thermal management utilizing a vapor chamber

ABSTRACT

Thermal management systems for batteries utilize vapor chambers having wicking components therein. An exemplary thermal management system includes a vapor chamber containing a working fluid and wicking components. A plurality of battery cells are disposed at least partially in the vapor chamber. A cold plate is coupled to the vapor chamber, and a heat pump is coupled to the cold plate. A capillary tube may be utilized to facilitate movement of vapor and working fluid in the thermal management system. Via use of exemplary systems, improved thermal management for batteries is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/815,975 filed on Nov. 17, 2017, entitled “SYSTEMS AND METHODS FORBATTERY THERMAL MANAGEMENT UTILIZING A VAPOR CHAMBER”. U.S. applicationSer. No. 15/815,975 claims priority to, and the benefit of, U.S.Provisional Application Ser. No. 62/424,054 filed on Nov. 18, 2016,entitled “SYSTEMS AND METHODS FOR BATTERY THERMAL MANAGEMENT UTILIZING AVAPOR CHAMBER”. The entire contents of the foregoing application arehereby incorporated by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates to thermal management, and in particularto thermal management of battery packs.

BACKGROUND

Prior approaches to thermal management of battery packs and cells,particularly in vehicle applications, have attempted to provide rapidand well-controlled heating and/or cooling of battery packs as desired.However, these prior approaches have been limited in their ability tomaintain battery cells within a desirable temperature range duringoperation, to control maximum and minimum cell temperatures, to achievean operational setpoint temperature, or to ensure a limited range ofthermal variability between cells in a battery pack. Accordingly,improved systems and methods for thermal management of battery packs andother electrical devices remain desirable.

SUMMARY

In an exemplary embodiment, a thermal management system comprises avapor chamber comprising a housing, a wicking material, and a workingfluid; and a battery pack comprising a plurality of battery cells. Eachof the plurality of battery cells is disposed at least partially withinthe vapor chamber. Each battery cell contacts a portion of the wickingmaterial, and the working fluid changes phase within the vapor chamberin order to carry heat away from the battery cells.

In another exemplary embodiment, a method for thermal regulation of abattery pack comprises disposing a plurality of battery cells at leastpartially within a vapor chamber, the plurality of battery cells forminga battery pack, and the vapor chamber comprising a housing, a wickingmaterial, and a working fluid; and contacting each of the plurality ofbattery cells with at least a portion of the wicking material. Duringcharging or discharging of the battery pack, the working fluid changesphase within the vapor chamber in order to carry heat away from thebattery cells.

In another exemplary embodiment, a thermal management system for anindividual battery cell comprises a coldwell comprising a housing, awicking material, and a working fluid; and a battery cell disposed atleast partially within the coldwell such that the bottom of the batterycell contacts the wicking material. The interface between the batterycell and the housing is sealed to retain the working fluid within thehousing. The working fluid changes phase within the coldwell in order tocarry heat away from the battery cell.

In another exemplary embodiment, a thermal management system for abattery pack comprises a vapor chamber comprising a housing, a wickingmaterial, and a working fluid; a cold plate coupling the vapor chamberto a heat pump; the battery pack comprising a plurality of batterycells, each of the plurality of battery cells disposed at leastpartially within the vapor chamber; a condensation chamber coupled tothe cold plate; and a capillary tube linking the vapor chamber and thecondensation chamber. Each battery cell contacts a portion of thewicking material, and the working fluid changes phase within the vaporchamber in order to carry heat away from the battery cells.

The contents of this summary section are to be understood as asimplified introduction to the disclosure, and are not intended to beused to limit the scope of any claim.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the following description, appended claims, andaccompanying drawings:

FIG. 1A illustrates an exemplary thermal management system having a coldplate disposed below a vapor chamber, the vapor chamber fully enclosingthe battery cells, in accordance with an exemplary embodiment;

FIG. 1B illustrates an exemplary thermal management system having a coldplate disposed above a vapor chamber, the vapor chamber fully enclosingthe battery cells, in accordance with an exemplary embodiment;

FIG. 1C illustrates an exemplary thermal management system having a coldplate disposed below a vapor chamber, the vapor chamber partiallyenclosing the battery cells, in accordance with an exemplary embodiment;

FIG. 1D illustrates an exemplary thermal management system having a coldplate disposed above a vapor chamber, the vapor chamber partiallyenclosing the battery cells, in accordance with an exemplary embodiment;

FIG. 1E illustrates orientation independence for operation of anexemplary thermal management system in accordance with an exemplaryembodiment;

FIG. 1F illustrates an exemplary thermal management system utilizing acommon coolant path for a battery pack, power electronics, and anelectric motor in accordance with an exemplary embodiment;

FIG. 2A illustrates a honeycomb-like configuration for a wick structurein accordance with an exemplary embodiment;

FIG. 2B illustrates battery cells positioned partially within the wickstructure of FIG. 2A in accordance with an exemplary embodiment;

FIG. 2C illustrates a post-like configuration for a wick structure inaccordance with an exemplary embodiment;

FIG. 2D illustrates battery cells interspersed between the wickstructure of FIG. 2C in accordance with an exemplary embodiment;

FIG. 2E illustrates a serial weave configuration for a wick structure inaccordance with an exemplary embodiment;

FIG. 2F illustrates battery cells positioned partially within the wickstructure of FIG. 2E in accordance with an exemplary embodiment;

FIG. 2G illustrates battery cells positioned partially within a wickstructure having a parallel weave configuration in accordance with anexemplary embodiment;

FIG. 2H illustrates a tapering wick structure in accordance with anexemplary embodiment;

FIG. 2I illustrates a wick structure having a configuration depending onbattery cell location in a battery pack in accordance with an exemplaryembodiment;

FIG. 2J illustrates targeted thermal management of battery cellsdepending on battery cell location in a battery pack in accordance withan exemplary embodiment;

FIGS. 3A through 3D illustrate a dual-layer configuration for a wickstructure and integration of battery cells therewith in accordance withvarious exemplary embodiments;

FIGS. 4A through 4D illustrate a dual-layer configuration for a wickstructure and integration of battery cells therewith in accordance withvarious exemplary embodiments;

FIGS. 5A through 5D illustrate a dual-layer configuration for a wickstructure and integration of battery cells therewith in accordance withvarious exemplary embodiments;

FIG. 6 illustrates a single battery cell and associated coldwell inaccordance with an exemplary embodiment;

FIGS. 7A through 7C illustrate use of a vapor chamber and wickingcomponents for cooling of electronic devices in accordance with variousexemplary embodiments;

FIGS. 8A through 8C illustrate an exemplary thermal management systemutilizing capillary tubes in connection with a vapor chamber, thecapillary tubes having intake and return ends on a common side of thevapor chamber, in accordance with various exemplary embodiments;

FIGS. 9A through 9C illustrate an exemplary thermal management systemutilizing capillary tubes in connection with a vapor chamber, thecapillary tubes having intake and return ends on opposing sides of thevapor chamber, in accordance with various exemplary embodiments;

FIG. 9D illustrates use of capillary tubes to achieve a desiredcirculation of working fluid in a vapor chamber in accordance withvarious exemplary embodiments;

FIGS. 10A and 10B illustrate an exemplary thermal management systemutilizing capillary tubes in connection with a vapor chamber, thecapillary tubes leading to a condensation chamber, and the condensationchamber coupled to the vapor chamber via wicking posts, in accordancewith various exemplary embodiments;

FIGS. 11A and 11B illustrate an exemplary thermal management systemutilizing capillary tubes in connection with a vapor chamber, thecapillary tubes leading to a condensation chamber, and the condensationchamber linked to the vapor chamber via wicking posts and working fluidtubes, in accordance with various exemplary embodiments; and

FIGS. 12A through 12C illustrate use of wicking posts of varied heightsin a thermal management system, in accordance with various exemplaryembodiments.

DETAILED DESCRIPTION

The following description is of various exemplary embodiments only, andis not intended to limit the scope, applicability or configuration ofthe present disclosure in any way. Rather, the following description isintended to provide a convenient illustration for implementing variousembodiments including the best mode. As will become apparent, variouschanges may be made in the function and arrangement of the elementsdescribed in these embodiments without departing from the scope of theappended statements.

For the sake of brevity, conventional techniques for battery packconstruction, configuration, and use, as well as conventional techniquesfor thermal management, operation, measurement, optimization, and/orcontrol, may not be described in detail herein. Furthermore, theconnecting lines shown in various figures contained herein are intendedto represent exemplary functional relationships and/or physicalcouplings between various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system or related methods ofuse, for example a battery pack for an electric vehicle.

Various shortcomings of prior batteries, thermal management systems,and/or the like can be addressed by utilizing battery packs and relatedcomponents configured in accordance with principles of the presentdisclosure. For example, prior two-phase cooling approaches typicallyutilized an integrated heat pipe and/or fully immersed battery cells ina fluid, thus adding significant weight and reducing energy density.Other prior approaches using wicking fully encase each battery cell inwicking material, limiting vapor movement, restricting capillary forceto overcome gravity when cooling is provided below the battery pack,increasing cell spacing, and reducing volumetric and gravimetric energydensity significantly.

In contrast, exemplary systems and methods disclosed herein enableimproved energy densities at the battery pack level by eliminatingrestrictions on spaces and battery cell shapes, and by utilizinglightweight materials. Additionally, exemplary systems utilize aliquid-vapor phase change mechanism to ensure quick thermal response andmaximized heat transfer. Significantly, exemplary systems provideeffective thermal management in all orientations, includinggravity-favored, inclined, horizontal, and antigravity conditions.Moreover, a wide range of electrically insulating but thermallyconductive materials may be utilized for wicking materials and workingfluids. In addition, exemplary system enhance and/or target heattransfer at portions of (or specific locations in) a battery pack. Yetfurther, via use of a shared working fluid environment within a vaporchamber, thermal runaway of a particular battery cell in a battery packcan be addressed, minimized, and/or prevented.

A thermal management system in accordance with principles of the presentdisclosure may be configured with any suitable components, structures,and/or elements in order to provide desired dimensional, mechanical,electrical, chemical, and/or thermal properties.

A “battery pack” as used herein describes a set of any number of batterycells, interconnected in series or parallel or a combination of seriesand parallel, to provide energy storage and/or electric power to asystem as a single integrated unit. An example of a battery pack wouldbe an electric vehicle lithium-ion battery pack, which can consist ofthousands of cylindrical lithium ion battery cells.

A “battery cell” as used herein describes an electrochemical cell thatis capable of generating electrical energy from a chemical reaction.Some battery cells can be rechargeable by introducing a current throughthe cell. Battery cells come in different types, such as lead-acid,nickel cadmium, nickel hydrogen, nickel metal hydride, lithium ion,sodium nickel chloride (a.k.a. “zebra”), based on the chemical reactionused to generate the electric current. Because battery cells produceelectricity based on a chemical reaction, the temperature of the cellcan influence the efficiency at which the electricity is produced.Battery cells can also be fuel cells, such as hydrogen-oxide protonexchange membrane cells, phosphoric acid cells, or solid acid cells.Principles of the present disclosure may desirably be applied to a widevariety of battery cell types, and are not limited to a particularbattery cell chemistry, size, or configuration.

A “heat pump” as used herein describes a system that moves thermalenergy from one part of a system, known as a “heat source”, to anotherpart of the system, known as the “heat sink”, by the application of anexternal power source. Typically, the heat is transferred by themovement of a fluid cycling between the heat source and the heat sink.Examples include reversible two-phase refrigerant systems andsingle-phase ethylene-glycol systems.

A “vapor chamber” (or “heat pipe”) as used herein describes aheat-transfer device that combines the principles of both thermalconductivity and phase transition to efficiently manage the transfer ofheat between two interfaces.

With reference now to FIGS. 1A through 1D, in various exemplaryembodiments a thermal management system 100 comprises a vapor chamber110, a cold plate 130, and a heat pump 150. Cold plate 130 is disposedbetween, and thermally coupled to, vapor chamber 110 and heat pump 150.In some embodiments, cold plate 130 and heat pump 150 are separatecomponents. In other exemplary embodiments, a surface forming part ofheat pump 150 may be considered to function as cold plate 130. In yetother exemplary embodiments, a surface forming part of vapor chamber 110may be considered to function as cold plate 130. Moreover, thermalmanagement system 100 may comprise any other suitable componentsconfigured to support, guide, modify, and/or otherwise manage and/orcontrol operation of thermal management system 100 and/or componentsthereof, for example sensors, ports, seals, electrical controls, and/orthe like. Thermal management system 100 may be utilized to provideisothermal and/or near-isothermal conditions, for example for batterycells 112 disposed within (or partially within) vapor chamber 110.

In some exemplary embodiments, vapor chamber 110 is configured to fullycontain one or more battery cells 112, for example as illustrated inFIGS. 1A and 1B.

In other exemplary embodiments, vapor chamber 110 is configured topartially contain one or more battery cells 112, for example asillustrated in FIGS. 1C and 1D. In these exemplary embodiments, vaporchamber 110 is configured with various orifices, seals, and/or the likein order to at least partially receive one or more battery cells 112while effectively retaining a working fluid 115 within vapor chamber110. Moreover, in these exemplary embodiments, access to one end of eachbattery cell 112 (for example, for electrical wiring) is made easier ascompared to approaches where each battery cell 112 is fully containedwithin vapor chamber 110, while still providing adequate thermalregulation of each battery cell 112. Additionally, in these exemplaryembodiments, vapor chamber 110 may function to at least partiallyretain, secure, and/or align battery cells 112 with respect to oneanother, reducing and/or eliminating the need for other battery cell 112retention and/or alignment components.

With continued reference to FIGS. 1C and 1D, in certain exemplaryembodiments vapor chamber 110 is configured with various seals,retaining mechanisms, sealants, and/or the like, so that vapor chamber110 may receive a portion of multiple battery cells 112 while preventingleakage and/or evaporation of working fluid 115 from within vaporchamber 110. For example, in one exemplary embodiment vapor chamber 110comprises a rigid primary material overmolded with an elastomer, inorder to provide a compressible seal at the interface where each batterycell 112 is inserted into vapor chamber 110. In other exemplaryembodiments, o-rings or other mechanical sealing approaches may beutilized. Moreover, a suitable potting material may be utilized in orderto seal the joints between battery cells 112 and vapor chamber 110. Forexample, in various exemplary embodiments the joints between batterycells 112 and vapor chamber 110 may be sealed via a flexible orsemi-flexible potting material, adhesive, sealant, epoxy, or hot melt;the sealing material may be silicone, urethane, polyurethane, polyester,or polyamide based and/or may comprise any other suitable sealing and/oradhesive materials or compounds.

Vapor chamber 110 may be configured to receive any suitable portion ofthe length (and/or surface area, volume, or the like) of battery cells112. In various exemplary embodiments, for each battery cell 112, vaporchamber 110 may be configured to receive between about 10% of the lengthof battery cell 112 and about 90% of the length of battery cell 112. Inother exemplary embodiments, for each battery cell 112, vapor chamber110 may be configured to receive between about 20% of the length ofbattery cell 112 and about 50% of the length of battery cell 112.Moreover, vapor chamber 110 may be configured to receive a differentpercentage of a battery cell 112, for example depending on the locationof a battery cell 112 in a battery pack. In an exemplary embodiment,vapor chamber 110 may receive about 25% of the length of a battery cell112 disposed on the edge of a battery pack, and about 50% of the lengthof a battery cell 112 disposed generally in the middle of a batterypack. Moreover, vapor chamber 110 may be configured to receive anysuitable percentage of a battery cell 112 based at least in part on theamount of thermal regulation desired for that particular battery cell112. In this manner, battery cells 112 needing a higher degree ofcooling than other battery cells 112 may be adequately cooled.

In various exemplary embodiments, vapor chamber 110 comprises a sealedor resealable container formed of a durable material, for exampleplastic, metal, and/or the like. In some embodiments, vapor chamber 110comprises one or more of aluminum, steel, or the like. Vapor chamber 110may be formed via any suitable process or combination of processes, forexample overmolding, laser welding, and/or the like.

Vapor chamber 110 may be configured with one or more vents, accessports, and/or the like, for example in order to relieve pressuretherefrom, allow adjustment of the level of working fluid 115 therein,and/or the like. In some exemplary embodiments, vapor chamber 110 isconfigured with internal temperature and/or pressure sensors in order toallow for adjustment of the amount of working fluid 115 within vaporchamber 110 (for example, at intervals, at a particular temperatureand/or pressure threshold, in real time, etc.)

Vapor chamber 110 is configured to contain (or partially contain) one ormore items to be thermally managed, for example a plurality of batterycells 112. In various exemplary embodiments, within vapor chamber 110,battery cells 112 (or portions thereof) may be configured in anysuitable orientation, number, alignment, size, and/or shape, althoughbattery cells 112 are commonly configured with a generally cylindricalshape. In some exemplary embodiments, battery cells 112 are packed inoffset horizontal and/or vertical rows in order to obtain a high densityof battery cells 112 within vapor chamber 110. In most exemplaryembodiments, battery cells 112 are configured with a positive terminaland a negative terminal on a common end of a cylindrical batterystructure (for example, as illustrated in FIGS. 1A through 1D). In thismanner, in thermal management system 100 wiring of battery cells 112 isfacilitated, while still enabling effective thermal management ofbattery cells 112.

Vapor chamber 110 contains a selected amount of working fluid 115.Working fluid 115 may comprise any suitable material or combination ofmaterials, for example water, methanol, ethanol (ethyl alcohol),acetone, pentane, perfluoromethylcyclohexane, heptane, and/or the like.Working fluid 115 is desirably electrically insulating and/ornon-reactive with components utilized in battery cells 112. Workingfluid 115 is selected to enable efficient operation of vapor chamber110. In various exemplary embodiments, characteristics of working fluid115 which may be selected, adjusted, and/or optimized include: density,viscosity, surface tension, boiling point, latent heat of vaporization,reactivity to other components of thermal management system 100, and/orthe like.

In thermal management system 100, vapor chamber 110 may be filled with adesired amount of working fluid 115, for example an amount sufficient tosaturate all wicking material 120 contained within vapor chamber 110.Moreover, vapor chamber 110 may be filled with an amount of workingfluid 115 exceeding the amount needed to saturate wicking material 120.Moreover, the amount of working fluid 115 disposed within vapor chamber110 may be selected based on a desired level of thermal regulation forbattery cells 112, an anticipated rate of loss or leakage of workingfluid 115 from vapor chamber 110, and/or the like.

Vapor chamber 110 also contains a selected amount of wicking material120 configured to interact with the plurality of battery cells 112 andthe working fluid 115.

Wicking material 120 can be soaked in working fluid 115 and can be in ameshed, porous, or tree-like structure, or a combination of those, toprovide capillary action and maximized wettability for evaporation andcondensation.

In various exemplary embodiments, wicking material 120 comprises anelectrically insulating but thermally conductive material that iscompatible with working fluid 115. For example, wicking material 120 maycomprise various fabrics in a microporous structure, such as amorphoussilica fibers, glass fiber, nylon, polytetrafluoroethylene,polypropylene, polyethylene (of various densities and/or branchingconfigurations), and/or the like. Moreover, wicking material 120 maycomprise and/or be structured as powders, filaments, fibers, fabrics,meshes, mats, membranes, and/or the like.

In some embodiments, wicking material 120 has a contact angle betweenthe intersection of the liquid-solid interface and the liquid-vaporinterface of less than 90 degrees (i.e., wicking material 120 ishydrophilic). The contact angle is determined by a combination offactors, including surface tension and gravity. Wicking material 120also benefits from having a high capillary effect. A small change inmaterial structure/roughness/texture can lead to significant changes incapillary force. In various exemplary embodiments, characteristics ofwicking material 120 which may be selected, adjusted, and/or optimizedinclude: the effective radius of the wick material, permeability of thewick material (as a result of both particle size and porosity),cross-sectional area of the wick material, effective length of a heattransfer pathway, and/or the like.

Wicking material 120 may be configured to transport working fluid 115 atleast partially along, towards, and/or between battery cells 112 invapor chamber 110. For example, with reference to FIG. 1A, inembodiments where cold plate 130 is disposed below vapor chamber 110,wicking material 120 is operative to draw working fluid 115 at leastpartially upwards along the side of the battery cells 112, facilitatingtransfer of thermal energy from battery cells 112 into working fluid115. Additionally, as working fluid 115 returns to a liquid phase viacondensation (for example, along the top and/or sides of vapor chamber110, wicking material 120 is operative to draw working fluid 115 whichhas run down the sides of vapor chamber 110 back toward the center ofvapor chamber 110.

In various exemplary embodiments, wicking material 120 is configured toachieve a desired capillary velocity when utilized in connection withworking fluid 115. In some embodiments, wicking material 120 achieves acapillary velocity of up to about 7 mm/s. In other exemplaryembodiments, wicking material 120 achieves a capillary velocity ofbetween about 4 mm/s and about 7 mm/s. Moreover, in thermal managementsystem 100, wicking material 120 (together with working fluid 115) maybe configured to provide a capillary velocity sufficient to alloweffective thermal regulation of battery cells 112 by transporting asufficient ongoing flow of working fluid 115 into contact with batterycells 112.

In some exemplary embodiments, wicking material 120 extends less thanabout 10% of the distance along each battery cell 112. In otherexemplary embodiments, wicking material 120 extends less than about 25%of the distance along each battery cell 112. In still other exemplaryembodiments, wicking material 120 extends less than about 50% of thedistance along each battery cell 112. It will be appreciated that,because thermal management system 100 does not require wicking material120 to extend fully along each battery cell 112, significant weight andcost savings may be realized. However, in thermal management system 100,wicking material 120 may extend any suitable selected distance alongeach battery cell 112.

In various exemplary embodiments, wicking material 120 may beconstructed via any suitable process, for example solvent casting,sheet-form molding and transverse stretching, injection molding, and/orthe like. Moreover, characteristics of wicking material 120 may bevaried when manufactured and/or as utilized within vapor chamber 110.For example, in various exemplary embodiments wherein wicking material120 is injection molded, characteristics of wicking material 120 may bevaried from injection site to injection site, allowing for customizedand/or targeted thermal performance of the resulting wick structure. Forexample, wicking material 120 having a first material (or mix ofmaterials), density, porosity, level of capillary action, and/or thelike may be injected at a first injection site, and wicking material 120having a second material (or mix of materials), density, porosity, levelof capillary action, and/or the like may be injected at a secondinjection site. Moreover, when manufactured via injection molding,wicking material 120 may be configured with a thickness of down to about0.75 mm, allowing wicking material 120 to be disposed between batterycells 112 in vapor chamber 110 while still permitting battery cells 112to be located very close together.

Cold plate 130 is configured to transfer thermal energy between vaporchamber 110 and heat pump 150. For example, when thermal managementsystem 100 is utilized to cool battery cells 112 in vapor chamber 110,cold plate 130 receives thermal energy from vapor chamber 110 and passesthe thermal energy to heat pump 150. Conversely, when thermal managementsystem 100 is utilized to warm battery cells 112 in vapor chamber 110(for example, when thermal management system 100 forms part of a vehicleplaced in a cold ambient environment), cold plate 130 receives thermalenergy from heat pump 150 and passes the thermal energy to vapor chamber110. Cold plate 130 may comprise any suitable durable and thermallyconductive material, for example anodized aluminum.

In an exemplary embodiment, cold plate 130 is configured withminichannel and/or microchannel cooling. Channels formed within and/oron cold plate 130 may be of any suitable size and/or geometry, forexample circular, rectangular, circular with “teeth” or otherprotrusions, trapezoidal, and/or the like. Cold plate 130 may beconfigured with channels for fluid flow only on the side of cold plate130 interfacing with heat pump 150, only on the side of cold plate 130interfacing with vapor chamber 110, or on both sides of cold plate 130.The channels on cold plate 130 are configured to cause and/or maintainturbulent fluid flow therethrough in order to maximize associated heattransfer.

In various exemplary embodiments, heat pump 150 is operative to removeheat from (or, in a heating mode, provide heat to) cold plate 130, forexample via pumped circulation of a coolant such as water, water-glycolmixtures, hydro-flourocarbon refrigerant liquids, and/or the like. Heatpump 150 may comprise any suitable pumps, impellers, valves, hoses,tubes, radiators, and/or the like, as is known in the art, in order totransfer heat to and/or from cold plate 130.

With reference again to FIGS. 1A and 1C, in various exemplaryembodiments, thermal management system 100 may be configured and/ororiented such that cold plate 130 is disposed below vapor chamber 110.With reference to FIGS. 1B and 1D, in various exemplary embodiments,thermal management system 100 may be configured and/or oriented suchthat cold plate 130 is disposed above vapor chamber 110. Moreover, itwill be appreciated that in many exemplary embodiments, the relationshipbetween cold plate 130 and vapor chamber 110 may be changed, for examplevia turning thermal management system 100 upside down, placing thermalmanagement system 100 on its side or on a slope relative to horizontal,and/or the like. Accordingly, with reference to FIG. 1E, thermalmanagement system 100 is configured to provide appropriate coolingand/or heating capabilities to items contained within vapor chamber 100,regardless of the orientation of thermal management system 100. Statedanother way, thermal management system 100 does not rely on anyparticular orientation with respect to gravity in order to functioneffectively. In contrast, prior approaches to vapor-based coolingtypically relied heavily on gravity for condensation and fluid return,and would fail to operate properly in the absence of gravitationalassistance. It will be appreciated that the orientation-independencefeatures of exemplary systems as disclosed herein are highly desirablein non-stationary energy storage systems such as electric vehicles, assuch systems are often operated in a tilted orientation. For example,thermal management system 100 is configured to function effectively whenutilized in an electric automobile, even when the automobile istraveling or parked uphill or downhill. Moreover, thermal managementsystem 100 is configured to function effectively when utilized in anelectric airplane, drone, or the like, even when the orientation ofthermal management system 100 is changing due to climbing, descending,banking during a turn, or the like.

During operation of thermal management system 100, at least two heattransfer pathways are operable in order to accomplish optimalperformance. Primary heat transfer is achieved by an external heat pump150, transporting heat away from/to battery cells 112 via a fluid (forexample, a water-glycol fluid or the like). Within vapor chamber 110,heat transfer is facilitated by liquid-vapor phase change inside voidsand/or cavities contained in and/or formed by wicking material 120.During a cooling mode of thermal management system 100, a quick thermalresponse is established via latent heat of vaporization and workingfluid 115 inside wicking material 120 vaporizes into vapor space 117 (asused herein, “vapor space” may refer to the space within vapor chamber110 that is not occupied by a solid or a liquid). Heat pump 150 carryingaway the heat causes the vapor to condense, and wicking material 120exerts capillary forces to pull back the condensate to the evaporationsites, thus repeating the above cycle. During a battery preheating modeof thermal management system 100, heat pump 150 serves as a heat sourcesupplying heat to vapor chamber 110. The vapor space within vaporchamber 110 operates as a thermosiphon or thermosiphons transferringheat to the walls of the battery cells 112. Large latent heat ofvaporization accelerates the preheating process, which is beneficial incold climates.

With momentary reference to FIG. 1F, principles of the presentdisclosure also contemplate an integrated thermal management system foran electric vehicle whereby a battery pack, power electronics, and amotor or generator may be cooled or heated via a unified systememploying two-phase cooling for the battery pack, power electronics, andmotor or generator. In some exemplary embodiments, a heat pump 150circulates a fluid (such as propylene glycol or the like) to interfacein order with battery pack 151, power electronics 152, and electricmotor 153 (moreover, battery pack 151, power electronics 152, andelectric motor 153 may be positioned in any order with respect to oneanother regarding fluid circulated by heat pump 150). In still otherexemplary embodiments, battery pack 151, power electronics 152, andelectric motor 153 are coupled to heat pump 150 each via a dedicatedfluid line, but share a common fluid reservoir. In various exemplaryembodiments, each of battery pack 151, power electronics 152, andelectric motor 153 are at least partially cooled via two-phase coolingutilizing a working fluid and/or wicking materials as disclosed herein.

In thermal management system 100, wicking material 120 may be configuredas desired, for example in order to achieve a particular level ofthermal performance, volumetric energy density, mechanical retentionand/or immobilization of battery cells 112, and/or the like. Forexample, wicking material 120 may be configured to at least partiallyretain battery cells 112 at particular locations within vapor chamber110 and/or with respect to one another.

With additional reference now to FIGS. 2A and 2B, in some exemplaryembodiments, wicking material 120 is configured with a honeycomb-likestructure. In these exemplary embodiments, wicking material 120 isconfigured as contact rings 210 that have heat flux contact areas 220that conduct heat from battery cells 112 (battery cells 112 beingindividually placed in each contact ring 210) to vapor paths 230 betweencontact rings 210. In FIG. 2A, contact areas 220 are shown as segmentsof contact rings 210, but a contiguous surface within a contact ring 210could also be utilized. Contact ring 210 shapes other than circularcould be used, especially if battery cells 212 are not cylindrical (forexample, rectangular cells). The area of contact between contact areas220 and battery cells 112 can be adjusted by changing the geometry ofthe contact rings 210 for optimized heat transfer. FIG. 2B illustrateswicking material 120 with cylindrical battery cells 112 positioned insome of the contact rings 210. In most cases of actual use, all contactrings 210 would have corresponding battery cells 112 inserted. Contactrings 210 can be formed from straight wall segments, as shown, or besmoothly circular with no corners. Vapor paths 230 can be triangular forefficient stacking arrangement of contact rings 210, or any othersuitable shape. Moreover, the thickness of wicking material 120 incontact rings 210 may vary within contact rings 210 and/or from ring toring. For example, the portions of contact rings 210 that fall directlybetween adjacent battery cells 112 may be thinner, while the portions ofcontact rings 210 that form the edges of vapor paths 230 may be thicker.In this manner, battery cells 112 may be placed close to one anotherwhile a sufficient amount of wicking material 120 remains in contact (orclose proximity) with each battery cell 112 in order to provide adesired level of thermal performance.

With reference now to FIGS. 2C and 2D, in various exemplary embodiments,wicking material 120 is configured as a plurality of post-likestructures. In some embodiments, posts 211 are formed from wickingmaterial 120 in a three-sided post shape, patterned so that there arevapor spaces 231 between posts 211 and between battery cells 112. Posts211 can include indents or other shapes to fit securely to the shape ofbattery cells 112. The three-sided shape of posts 211 allows for anefficient stacking arrangement of battery cells 112. However, anysuitable shape for posts 211 may be utilized; moreover, a post 211 maydiffer in size, shape, materials, or other characteristics from anotherpost 211 in order to provide a selected level of thermal performance ata particular location within vapor chamber 110.

Moreover, any suitable number of posts 211 may be utilized in vaporchamber 110. For example, in vapor chamber 110, each battery cell 112may be in contact with at least one post 211, or at least two posts 211,or at least three posts 211, or at least four posts 211. Additionally,in vapor chamber 110, certain posts 211 (and/or all posts 211) mayextend from an inner surface of vapor chamber 110 all the way to acorresponding inner surface on the opposite side of vapor chamber 110 inorder to facilitate effective movement of working fluid 115, regardlessof orientation of vapor chamber 110.

In some exemplary embodiments (for example, where battery cells 112 aregenerally circular) posts 211 may be sized and/or configured to fitentirely into spaces that exist between battery cells 112 when batterycells 112 are packed as close as geometrically possible. In this manner,thermal management system 100 is configured to achieve improved thermalcontrol of battery cells 112 without adding any volume to the spacingbetween battery cells 112.

With reference now to FIGS. 2E and 2F, in various exemplary embodiments,wicking material 120 is configured with a serial weave pattern. Theserial weave walls 212 of wicking material 120 are patterned such thateach battery cell 112 is partially contacted while leaving vapor spaces232 for vapor return. The serial weave pattern can be from a singlecontiguous strip of wicking material 120, or from separate strips.Moreover, the thickness or other characteristics of the serial weavewalls 212 may vary, for example depending on the location of a batterycell 112 within vapor chamber 110.

Turning now to FIG. 2G, in various exemplary embodiments, wickingmaterial 120 is configured with a parallel weave pattern. The parallelweave walls 213 of wicking material 120 are patterned such that eachbattery cell 112 is are partially contacted while leaving vapor spaces232 for vapor return. The parallel weave pattern can be from a singlecontiguous strip of wicking material 120, or from separate strips.Moreover, the thickness or other characteristics of the parallel weavewalls 213 may vary, for example depending on the location of a batterycell 112 within vapor chamber 110.

With reference now to FIG. 2H, in various exemplary embodiments wickingmaterial 120 may be configured with a tapered and/or variable thickness.For example, wicking material 120 may vary in thickness as it extendsalong a battery cell 112. In some exemplary embodiments, wickingmaterial 120 may decrease in thickness as it extends from the base of abattery cell 112 toward the distal end of that battery cell 112. In thismanner, the amount of wicking material 120 to be used within vaporchamber 110 may be reduced, offering weight and cost savings. Wickingmaterial 120 may taper evenly; alternatively, wicking material 120 maytaper in a step-wise or uneven manner, as desired. Moreover, wickingmaterial 120 may be tapered in order to provide a desired balancebetween providing a particular amount of capillary action near batterycells 112 while providing a desired amount of available vapor space.

In addition to variable thickness, wicking material 120 may vary inother characteristics as it extends along a battery cell 112. Forexample, portions of wicking material 120 disposed near the base of abattery cell 112 may be configured to efficiently transfer working fluid115 along battery cell 112 via capillary action, while portions ofwicking material 120 disposed further along battery cell 112 may beconfigured to facilitate efficient vaporization of working fluid 115.

In thermal management system 100, wicking material 120 may be configuredto at least partially account for and/or manage the different thermalconditions experienced by various battery cells 112 depending on theirlocation within vapor chamber 110. Turning now to FIG. 2I, in someexemplary embodiments wicking material 120 is disposed in a non-uniformmanner within vapor chamber 110 and/or with respect to a particularbattery cell 112. For example, wicking material 120-A may extend a firstdistance along a side of battery cell 112 that is adjacent to a sidewall of vapor chamber 110. Wicking material 120-B may extend a second,longer distance along a side of battery cell 112 that is adjacent toanother battery cell 112 in vapor chamber 110 (and/or disposed furtherfrom an edge of vapor chamber 110). Stated another way, vapor chamber110 may be configured to provide additional wicking material 120 forbattery cells 112 (and/or sides of battery cells 112) that are at leastpartially surrounded by other battery cells 112 within vapor chamber110.

Additionally, in various exemplary embodiments, characteristics otherthan shape and size may be varied for wicking material 120 in connectionwith a particular battery cell 112. For example, porosity of wickingmaterial 120 in contact with a first battery cell 112 may vary from theporosity of wicking material 120 in contact with a second battery cell112. In this manner, battery cells 112 may be provided with differentcooling and/or heating rates that are better aligned to the particularlocations within vapor chamber 110, ensuring more uniform thermalconditions across battery cells 112. Stated another way, thermalmanagement system 100 may be configured with targeted zone coolingand/or heating capabilities. The amount, shape, and properties ofwicking material 120 may vary with the heat profile of a particularbattery pack, vary the available rate of removal of heat in a particularportion of a battery pack, and/or the like.

With reference now to FIG. 2J, in various exemplary embodiments, thermalmanagement system 100 is configured to provide differing rates ofthermal transfer to battery cells 112, depending at least in part on thelocation of a particular battery cell 112 in a battery pack. Forexample, as illustrated in FIG. 2J, in an exemplary battery pack certainbattery cells 112 may be considered “edge” cells, for example batterycells 112 disposed at least partially adjacent to a side of the batterypack (and/or having a path to the side of the battery pack which is notinterrupted by another battery cell 112). Moreover, in an exemplarybattery pack certain battery cells 112 may be considered “inner” cells,for example battery cells 112 disposed adjacent to at least one edgecell but not adjacent to a side of the battery pack. Yet further, in anexemplary battery pack certain battery cells 112 may be considered“center” cells, for example battery cells 112 disposed adjacent only toinner cells and/or other center cells. In various exemplary embodiments,thermal management system 100 may be configured to provide a higher rateof thermal transfer to center battery cells 112 as compared to innerbattery cells 112 and/or edge battery cells 112 (for example, via use ofadditional wicking material 120, use of wicking material 120facilitating more efficient vaporization of working fluid 115, deeperinsertion of battery cell 112 into vapor chamber 110, and/or the like).Moreover, thermal management system 100 may be configured to provide ahigher rate of thermal transfer to inner battery cells 112 as comparedto edge battery cells 112. Additionally, system 110 may be configured toprovide differing rates of thermal transfer as between two specificcenter battery cells 112, or as between two specific inner battery cells112, and/or as between two specific edge battery cells 112. It will beappreciated that the foregoing examples of targeted thermal managementof battery cells 112 are merely illustrative; stated generally, inthermal management system 100 battery cells 112 needing additionalheating and/or cooling may be provided with such additional thermaltransfer in order to provide conditions more closely approximatingisothermal conditions within vapor chamber 110.

Additionally, thermal management system 100 may be configured to providediffering rates of thermal transfer to battery cells 112 based at leastin part on a direction and/or path of thermal fluid flow associated withcold plate 130. For example, during operation of heat pump 150, thermalfluid is pumped across cold plate 130, for example in a serpentine-likepath. When thermal management system 100 is operative in a cooling mode,the thermal fluid gains heat as it traverses cold plate 130.Accordingly, the thermal fluid is at a higher temperature when it exitscontact with cold plate 130 as compared to when it begins contact withcold plate 130. Accordingly, battery cells 112 disposed, with respect tocold plate 130, at or near the area where the thermal fluid beginscontact with cold plate 130 (“entry” cells), may be provided with adifferent configuration of associated wicking material 120 as opposed tobattery cells 112 disposed at or near the area where the thermal fluidexits contact with cold plate 130 (“exit” cells). This is because entrycells may obtain a higher degree of direct conductive cooling from coldplate 130 than exit cells. In this manner, via operation of thermalmanagement system 100, battery cells 112 in a battery pack mayexperience conditions closer to true isothermic conditions.

In thermal management system 100, in some exemplary embodiments wickingmaterial 120 comprises a single type, layer, and/or configuration ofmaterial. In other exemplary embodiments, wicking material 120 may beconfigured as multiple layers and/or segments or portions. Wickingmaterial 120 in a first portion may comprise a different material and/orcharacteristic from wicking material 120 in a second portion. Forexample, a wicking material 120 characteristic such as a pore size,material density, fiber thickness, and/or the like may differ fromportion to portion. In various exemplary embodiments, pore sizes inwicking material 120 may range from about 1 micrometer (μall) to about100 μm. In this manner, within vapor chamber 110, wicking action may beincreased in certain portions, while phase-change action may befacilitated in certain other portions. In this manner, distribution ofworking fluid 115 within vapor chamber 110 may be optimized in order tomore effectively cool battery cells 112.

With reference now to FIGS. 3A through 3D, in some exemplary embodimentswicking material 120 is configured with a first layer and a second layer(more generally, a first wicking portion 322 and a second wickingportion 326). First wicking portion 322 may be configured to rapidlyand/or effectively transport working fluid 115 to second portion 326(for example, a sideways direction with respect to a series of batterycells 112; i.e., for generally cylindrical battery cells 112, adirection generally perpendicular to the cylindrical axis). Firstwicking portion 322 may be configured with holes or apertures 323therethrough in order to fit between and/or among battery cells 112. Inthese exemplary embodiments, the ends of battery cells 112 may be indirect contact with cold plate 130, with no wicking material 120disposed therebetween. In this manner, conductive thermal transfer fromthe end of battery cells 112 to cold plate 130 may be facilitated, whilestill allowing for efficient distribution of working fluid 115 withinvapor chamber 110 via operation of wicking material 120.

Second wicking portion 326 may be configured to primarily facilitatedistribution of working fluid 115 in a second direction (for example,along the length of a particular battery cell 112) and/or to moreeffectively facilitate vaporization of working fluid 115. In someexemplary embodiments, second wicking portion 326 may be configured as aseries of generally triangular posts 327, each having an opening 328therethrough to function as a vapor path. Posts 327 may also have spaces329 between individual posts 327 in order to provide additional vaporpaths. By utilizing wicking material 120 configured with multipleportions, improved distribution of working fluid 115 may be realized,resulting in better thermal distribution within vapor chamber 110.

Turning now to FIGS. 4A through 4D, in some exemplary embodiments, afirst wicking portion 422 of wicking material 120 is configured to passunderneath and/or be disposed between battery cells 112 and a side, top,or bottom of vapor chamber 110. In these approaches, first wickingportion 422 may be configured absent any holes or apertures for batterycells 112 to pass through, and second wicking portion 426 may beconfigured in a suitable manner, for example similar to second wickingportion 326 (i.e., with posts 427 and openings 428). Moreover, firstwicking portion 422 may be configured to roughly approximate the outlineof a group of battery cells 112, as shown.

In yet other exemplary embodiments, a first wicking portion 522 ofwicking material 120 may be configured as a sheet or plane ofuninterrupted material, as illustrated in FIGS. 5A through 5D. Secondwicking portion 526 may be configured similarly to second wickingportion 326 and/or 426. Moreover, first wicking portion 322/422/522 andcorresponding second wicking portion 326/426/526 may be manufacturedseparately from one another. Alternatively, first wicking portion322/422/522 and corresponding second wicking portion 326/426/526 may bemanufactured together, for example by injection molding.

It will be appreciated that the multiple-portion approaches disclosed inFIGS. 3A through 5D are compatible with, and may be used together with,the various configurations and geometries for wicking material 120disclosed in connection with the discussion of FIGS. 2A through 2J.Moreover, it will be appreciated that, during operation of thermalmanagement system 100, first wicking portion 322/422/522 functions toprovide more uniform distribution of working fluid 115 within vaporchamber 110, particularly when vapor chamber 110 is disposed at aslanted and/or sideways orientation with respect to gravity.

As compared to prior thermal management approaches, principles of thepresent disclosure allow various advantages, for example improvedcooling performance, weight savings, and/or the like. For example, forthe embodiment illustrated in FIGS. 3A through 3D, the density of asingle post 327 is less than one quarter the density of aluminum, whilestill achieving at least 3 times the thermal performance. Additionally,the unique placement of posts 327 allows battery cell 112 spacing to begoverned by manufacturability of cell retainers rather than posts 327.Moreover, posts 327 can even accommodate the minimized spacing achievedwhen adjacent battery cells 112 touch one another. Stated another way,in thermal management system 100, battery cells 112 may be positioned toachieve the maximum possible volumetric efficiency of 90.69% (forcylindrical cells), while still allowing for effective thermalmanagement of battery cells 112 via operation of vapor chamber 110,wicking material 120, and so forth. Moreover, in thermal managementsystem 100, battery cells 112 may be positioned to achieve a volumetricefficiency of between 80% and 90.69%, or more preferably between 85% and90.69%, and still more preferably between 88% and 90.69%.

In various exemplary embodiments, the mass of posts 327 associated witha particular battery cell 112 in vapor chamber 110 is less than 0.5% ofbattery cell 112, permitting extremely high energy densities. In someexemplary embodiments, the mass of all wicking material 120 within vaporchamber 110 is less than 0.5% of the mass of all battery cells 112 thatare thermally managed via operation of vapor chamber 110. Moreover, invarious exemplary embodiments, the mass of all wicking material 120within vapor chamber 110 is between about 0.1% and about 1% of the massof all battery cells 112 that are thermally managed via operation ofvapor chamber 110.

With reference now to FIG. 6 , in various exemplary embodiments,principles of the present disclosure may be applied at the level of anindividual battery cell 112, rather than at the level of a pack ofbattery cells 112. For example, in order to provide thermal managementof a battery cell 112, in some exemplary embodiments a two-phase thermalmanagement system is coupled to an end of a single battery cell 112. Inan exemplary embodiment, a “coldwell” 610 is coupled to an end ofbattery cell 112, forming a fully enclosed space between the outer wallof coldwell 610 and the end of battery cell 112. Coldwell 610 containswicking material 120 disposed at least partially along the bottom andedges thereof; within coldwell 610, wicking material 120 is also incontact with the end of battery cell 112. Coldwell 610 contains aselected amount of working fluid 115. During operation, working fluid115 vaporizes at or near the interface between battery cell 112 andwicking material 120, and condenses generally in the “condensationregion” illustrated in FIG. 6 . Depending on the orientation of batterycell 112 and coldwell 610, capillary action (and/or gravity) drawscondensed working fluid 115 through wicking material 120 back towardsthe surface of battery cell 112, and the cycle repeats. Coldwell 610 maybe coupled to any suitable additional components (for example, a heatpump, fan, or the like) in order to remove heat therefrom or provideheating thereto. It will be appreciated that a coldwell 610 may becoupled to each battery cell 112 in a battery pack (or only a portion ofbattery cells 112 in a battery pack) in order to provide thermalregulation; moreover, characteristics of an associated coldwell 610 mayvary among battery cells 112 in a battery pack.

With reference now to FIGS. 7A through 7C, in various exemplaryembodiments, two-stage cooling principles of the present disclosure maybe utilized to provide thermal management to power stage components,such as battery pack controller circuitry, motor or generator electroniccontrol systems, and/or the like. FIGS. 7A through 7C show an example ofa two-stage cooling system utilized for cooling power stage components730, such as battery pack controller circuitry or motor/generatorelectronic control systems. External heat pump 750 provides cooling tothe entire power stage system. The power stage components 730 are atleast partially encompassed by a wicking material 720 that wicks aworking fluid to the power stage components 730 to provide cooling.Channels 760 can be incorporated in wicking material 720 to act as vaporchambers connecting the power stage components 730 to the external heatpump 750, allowing the vapor to be cooled and condensed by external heatpump 750 for liquid phase return to power stage components 730 bycapillary action through wicking material 720.

When in operation, vapor chamber 110 has upper limits to its heattransport capability governed by one or more factors. In some exemplaryembodiments, operation of vapor chamber 110 may be affected by thefollowing factors: a capillary limit, entrainment limit, boiling limit,sonic limit, and/or viscous limit. Capillary limit indicates the drivingpressure for liquid circulation, i.e., the ability of wicking material120 to transfer working fluid 115 via capillary action. Entrainmentlimit: in operation, the vapor velocity increases with temperature andmay be sufficiently high to produce shear force effects on the returnflow of liquid working fluid 115 from a condensation region to avaporization region, which causes entrainment of the liquid by thevapor, leading to fluid flow shortages and eventually to dry out ofportions of wicking material 120. Boiling limit: a point reached whentemperature difference exceeds the degree of superheat sustainable inrelation to nucleate boiling conditions; the onset of boiling withinwicking material 120 interferes with liquid circulation of working fluid115 and can lead to dry out of portions of wicking material 120. Soniclimit: at a temperature above the vapor pressure limit, the vaporvelocity can be comparable with sonic velocity (i.e., Ma close to, equalto, and/or exceeding 1) and the vapor flow becomes “choked”, preventingfurther increases in heat transfer capacity. A viscous limit typicallyoccurs at low temperature, and represents a measure of cold startcapability of vapor chamber 110. In various exemplary embodiments,operation of thermal management system 100 is governed by an associatedcapillary limit; stated another way, thermal management system 100 isconfigured to reach a capillary limit prior to reaching any other limit.

Table 1 below presents exemplary operational values for an exemplarythermal management system 100 wherein cold plate 130 is disposed belowvapor chamber 110 (i.e., an “antigravity” orientation, for example asillustrated in FIGS. 1A and 1C). At lower operating temperatures, theviscous limit is dominant and thus restricts the vapor flow. Thesaturated temperature of vapor chamber 110 is optimally designed, andthus in operation the capillary limit becomes the limiting factor. Inthermal management system 100, components are configured to overcome notonly gravity but also impart a sufficient force to pull working fluid115 back to a desired height along battery cells 112. As shown in Table1, in this exemplary embodiment, maximum performance of vapor chamber110 ranges from about 9.26 W to about 28.03 W of heat loss at batterycell 112 level, depending on different configurations and operatingconditions. Accordingly, in various exemplary embodiments, thermalmanagement system 100 may achieve between about 0.018 K/W to about 0.054K/W thermal resistance (or about 617.33 watts per meter-kelvin (W/mK) toabout 5,606 W/mK effective thermal conductivity) with near isothermalconditions within vapor chamber 110.

TABLE 1 Vapor Chamber 110 Operating Limits - Exemplary ConfigurationVapor Chamber Operating Limits Operating Temperature (C.) (W) LowerLimit ° C. Optimal ° C. Upper Limit ° C. Capillary Limit 9.3 28.03 49.16Entrainment Limit 184.27 826.79 1596.86 Boiling Limit 7897.12 373.5976.01 Sonic Limit 15.81 340.27 1905.87 Viscous Limit 0.04 31.41 481.79

As compared to prior battery thermal management systems, thermalmanagement system 100 achieves an extremely high level of cooling at thebattery cell 112 level. In some exemplary embodiments, thermalmanagement system 100 provides about 1500 W/mK of thermal transfer atthe battery cell 112 level (i.e., a thermal transfer rate comparable todirect contact with diamond). In other exemplary embodiments, thermalmanagement system 100 provides thermal transfer at the battery cell 112level of between about 500 W/mK (i.e., a level of thermal transferslightly above that of direct contact with copper) to about 2000 W/mK(i.e., a level of thermal transfer about 500% that of direct contactwith copper). Moreover, it will be appreciated that in various exemplaryembodiments, thermal management system 100 provides a level of thermaltransfer at the battery cell 112 level that is equivalent to betweenabout 3 times greater and about 5 times greater than direct contact withvarious solid materials commonly utilized for conductive heat transfer,such as aluminum, copper, or the like.

Moreover, as compared to prior approaches, principles of the presentdisclosure enable a high energy density at the battery pack level. Forexample, vapor chamber 110 may be configured to be lightweight. Thiscontributes to much higher energy density at the battery pack level. Forinstance, the mass of vapor chamber 110 at battery pack level in variousexemplary embodiments ranges from about 1.45 kg to about 2.9 kg (for a98 kWh battery pack) depending on the configuration of wicking material120 in vapor chamber 110. It will be appreciated that total volumetricenergy density can be maximized with high energy density cylindricalcells, as the posts of wicking material 120 do not occupy any additionalspace. Consequently, there are no losses in volumetric energy density.Compared to various existing approaches, when utilizing identicalbattery cells of identical capacity, an exemplary embodiment of thermalmanagement system 100 achieves at least an additional 56 Wh/L ofvolumetric energy density (an increase of >12%), and advantages ofprinciples of the present disclosure only increase for packs of highercapacity.

For example, in a volume of approximately 105 L, an exemplary batterypack can achieve >55 kWh of storage, whereas prior approaches utilizingthe same battery chemistry and battery cell dimensions could onlyachieve about 46 kWh. In various exemplary embodiments, in thermalmanagement system 100 battery cells 112 may be disposed with a cellspacing of between about 0 mm (i.e., adjacent battery cells 112 touchone another) to about 2 mm. In contrast, prior cooling approaches oftenrequire battery cells to be spaced at least 2 mm apart.

Moreover, as compared to prior two-phase cooling approaches, gravimetricenergy density in exemplary embodiments of thermal management system 100is better. In some exemplary embodiments, improvements in gravimetricenergy density may range from about 0.5% to about 15%; in otherexemplary embodiments, improvements in gravimetric energy density mayrange from about 5% to about 15%; and in yet other exemplaryembodiments, improvements in gravimetric energy density may range fromabout 8% to about 12%. Moreover, as compared to prior conductivelycoupled and single phase cooling solutions, exemplary systems disclosedherein offer significantly higher gravimetric and volumetric energydensities.

In accordance with principles of the present disclosure, an exemplarybattery thermal management system may desirably be utilized inconnection with an electric vehicle or item of mobile industrialequipment, for example an automobile, tractor, truck, trolley, train,van, quad, golf cart, scooter, boat, airplane, drone, forklift,telehandler, backhoe, and/or the like.

In various exemplary embodiments, thermal management system 100 mayutilize additional structures and/or components to facilitate movementand/or distribution of vapor and working fluid 115. With reference nowto FIGS. 8A through 8C, in various exemplary embodiments a thermalmanagement system 100 may be configured to use one or more capillarytubes 114. Capillary tubes 114 facilitate condensation of working fluid115 from vapor to liquid state. Additionally, capillary tubes 114facilitate more even distribution of working fluid 115 in thermalmanagement system 100. Capillary tubes 114 also provide improved heattransfer from (and/or to) battery cells 112 due to oscillation resultingin movement of working fluid 115 through capillary tubes 114; statedanother way, capillary tubes 114 facilitate forced convection inaddition to phase change heat transfer. Moreover, capillary tubes 114convert a portion of thermal energy arising from battery cells 112 intokinetic energy of working fluid 115 slugs and vapor bubbles. Yetfurther, capillary tubes 114 facilitate a stable and/or generallyuniform vapor pressure in thermal management system 100 during operationthereof; stated another way, in thermal management system 100 capillarytubes facilitate a reduced pressure drop from evaporator to condenser.

In various exemplary embodiments, a capillary tube 114 comprises athermally conductive material, such as aluminum, copper, and/or thelike. Capillary tube 114 may be electrically insulated and/or isolated,for example via a dielectric coating such as aluminum oxide. In someexemplary embodiments, capillary tube 114 may comprise a durablematerial such as plastic. In general, a capillary tube 114 may be formedfrom a material that is compatible with and/or non-reactive with workingfluid 115. Capillary tube 114 may comprise a circular tube;alternatively, capillary tube 114 may have an oval cross-section, arectangular cross-section, or other suitable shape. A capillary tube 114may have multiple intake portions leading to a common main portion(i.e., in an arrangement similar to tributaries joining a river).Moreover, a capillary tube 114 may have a common main portion leading tomultiple return portions (i.e., in an arrangement similar to a riverfanning out into multiple paths at a delta). Stated another way, acapillary tube 114 may have a single intake end and/or return end;alternatively, a capillary tube 114 may have multiple intake ends and/orreturn ends. Moreover, capillary tube 114 may vary in diameter, wallthickness, or other characteristics along its path, as desired.

A diameter for a particular capillary tube 114, a wall thickness for aparticular capillary tube 114, and/or the number of capillary tubes 114utilized in a particular thermal management system 100, may be selectedbased on one or more of: a specified heat load in thermal managementsystem 100, length of capillary tube 114, surface tension of workingfluid 115, inclination angle of capillary tube 114, vapor pressure invapor chamber 110, number of turns in capillary tube 114, a desiredhorizontal and/or vertical flow rate through capillary tube 114, numberof battery cells 112 contained at least partially within vapor chamber110, and/or the like. Moreover, a capillary tube 114 may be configuredwith internal and/or external components, for example a textured innerand/or outer surface, in order to facilitate condensation of vaporwithin capillary tube 114 and/or transport of working fluid 115 throughcapillary tube 114.

In an exemplary embodiment, capillary tube 114 comprises copper tubinghaving an inner diameter of 3 mm. In another exemplary embodiment,capillary tube 114 comprises copper tubing having an inner diameter of 5mm. In various exemplary embodiments, capillary tube 114 comprises ametal tubing having an inner diameter not exceeding 12 mm. In yetanother exemplary embodiment wherein working fluid 115 comprises ethanoland the interior of vapor chamber 110 is subject to 0.18 bar of vaporpressure (resulting in a boiling point of ethanol of about 40 degreesCelsius), capillary tube 114 is configured with an inner diameter of 3.6mm.

During operation of thermal management system 100, condensation withincapillary tubes 114 results in formation of “slugs” of working fluid 115separated by bubbles of vapor/air. Bubble and slug formation incapillary tubes 114 leads to perturbations in the operation of fluidflow therethrough. Accordingly, in a thermal management system 100configured with capillary tubes 114, the configuration of capillarytubes 114 may be adjusted to obtain a desired “filling ratio”, i.e., aratio of amount of working fluid 115 to vapor/air in capillary tubes114. A higher ratio of bubbles to slugs (i.e., a lower overall amount ofworking fluid 115 in capillary tube 114) is typically achieved via asmaller diameter for capillary tube 114 and results in lower mass flowof working fluid 115 for sensible heat transfer. A higher ratio of slugsto bubbles (i.e., a higher overall amount of working fluid 115 incapillary tube 114) is typically achieved via a larger diameter forcapillary tube 114 and results in lower oscillations while reducingpumping action and heat transfer. Accordingly, capillary tube 114 may besized to obtain a desired trade-off for optimizing operation of thermalmanagement system 100, for example a desired balance between pumpingaction and mass flow.

Capillary tubes 114 may be disposed within thermal management system 100in various ways. In an exemplary embodiment, thermal management system100 utilizes one or more capillary tubes 114 having an intake end and areturn end disposed on a common side of vapor chamber 110. A capillarytube 114 passes into, passes through, and/or is thermally coupled to acondensation chamber 140. When thermal management system 100 isoperative, vapor in capillary tube 114 condenses into the liquid form ofworking fluid 115, leading to alternating bubbles of vapor/air and slugsof working fluid 115 in capillary tube 114. Vapor pressure generated invapor chamber 110 forces the slugs through the capillary tube 114,resulting in outflow of working fluid 115 from the return end ofcapillary tube 114 and thus depositing condensed working fluid 115 atthe base of posts 211.

Turning now to FIGS. 9A through 9C, in some exemplary embodimentsthermal management system 100 utilizes one or more capillary tubes 114having an intake end or ends on a first side of vapor chamber 110, and areturn end or ends on an opposing side (or orthogonal side, or, ingeneral, any different side) of vapor chamber 110. For example, withreference to FIG. 9C, a thermal management system 100 having a generallyrectangular vapor chamber 110 may be configured with two capillary tubes114. The intake end of the first capillary tube 114 and the return endof the second capillary tube 114 may be positioned generally on one sideof rectangular vapor chamber 110. On the opposite side of the rectangleare disposed the return end of the first capillary tube 114 and theintake end of the second capillary tube 114. In this manner, a supply offreshly condensed working fluid 115 is introduced to two opposing sidesof vapor chamber 110.

It will be appreciated that, in various exemplary embodiments, multiplecapillary tubes 114 may be utilized to direct flow of working fluid 115in thermal management system 100; such arrangements may be symmetrical,asymmetrical, looped, or otherwise arranged as desired to distributeworking fluid 115 within thermal management system 100. For example,with momentary reference to FIG. 9D, in one exemplary embodiment thermalmanagement system 100 may be configured with a 4-sided vapor chamber 110and may utilize 4 capillary tubes 114. A first capillary tube 114-A hasan intake end on side S1 of vapor chamber 110, and a return end onadjacent side S2. A second capillary tube 114-B has an intake end onside S2 and a return end on adjacent side S3, a third capillary tube114-C has an intake end on side S3, and a return end on adjacent sideS4, and finally, fourth capillary tube 114-D has an intake end on sideS4, and a return end on adjacent side S1. During operation of thermalmanagement system 100, working fluid 115 is circulated in a round-robinmanner through the four capillary tubes 114, leading to a more evendistribution of working fluid 115 in thermal management system 100 andthus affording more balanced thermal management of battery cells 112utilized therein.

With reference now to FIGS. 10A and 10B, in some exemplary embodimentsthermal management system 100 is configured with capillary tubes 114, aswell as with vapor/fluid passageways or paths between vapor chamber 110and a condensation chamber 140. In these configurations, vapor iscollected via capillary tubes 114 and introduced into a common pool ofworking fluid 115 within condensation chamber 140. In condensationchamber 140, working fluid 115 is distributed and pooled acrosscondensation chamber 140 via operation of gravity and via surfacetension of working fluid 115 (i.e., similar to how a fluid distributesacross the bottom of a container as the container is filled);additionally, working fluid 115 may be distributed within condensationchamber 140 responsive to acceleration, or responsive to inclination ofcondensation chamber 140 away from horizontal. Posts 211 extend into thepool of working fluid 115 contained in condensation chamber 140 andextract working fluid 115 via capillary action, raising working fluid115 into vapor chamber 110. Thereafter, working fluid 115 evaporates tocool battery cells 112 as discussed in various embodiments hereinabove.

It will be appreciated that in these exemplary embodiments, cold plate130 is configured with a plurality of apertures 131 to allow posts 211to pass through cold plate 130 and access working fluid 115 incondensation chamber 140. Stated another way, in these exemplaryembodiments cold plate 130 is configured as a perforated barrierdisposed between vapor chamber 110 and condensation chamber 140.However, it will be appreciated that cold plate 130 still remains sealedaround the apertures 131, such that coolant may pass through cold plate130 without leaking into vapor chamber 110 and/or intermingling withworking fluid 115.

In various exemplary embodiments, apertures 131 are sized to correspondto spaces between battery cells 112 in vapor chamber 110. Stated anotherway, apertures 131 may be sized in a manner that does not requireexpanded spacing between battery cells 112, thus allowing an exemplarybattery pack to maintain a desired energy density.

In various exemplary embodiments, apertures 131 are configured asgenerally circular holes when viewed perpendicular to the plane of coldplate 130. In other exemplary embodiments, apertures 131 are configuredto have the shape of one or more of a triangle, Reuleaux triangle,pseudotriangle, square, rectangle, oval, and/or combinations of thesame. In various exemplary embodiments, apertures 131 are configuredwith a diameter (and/or longest dimension) not exceeding 6 mm. In oneexemplary embodiment, apertures 131 comprises circular holes having adiameter of 4 mm.

It will be appreciated that, in thermal management system 100, apertures131 may be configured with different shapes and/or sizes from oneanother. For example, in thermal management system 100, a first aperture131 having a post 211 disposed therein may be configured as a circularhole having a diameter of 4 mm. A second aperture 131 that does not havea post 211 disposed therein may be configured as a circular hole havinga diameter of 2 mm. In another example, a first aperture 131 having apost 211 disposed therein may be configured as a roughlypseudotrianglular hole having a distance between vertices of about 5 mm.In this example, a second aperture 131 that does not have a post 211disposed therein may be configured as a circular hole having a diameterof 3 mm. Moreover, in thermal management system 100, any suitablecombinations of aperture 131 sizes and shapes may be utilized, forexample in a checkerboard, striped, staggered, or other suitablepattern, in order to provide for circulation of working fluid 115 andvapor within thermal management system 100.

In various exemplary embodiments, posts 211 are configured to begenerally flush with the edges of corresponding apertures 131. Statedanother way, a post 211 may fully fill or occupy the correspondingaperture 131 through which it is disposed. In some exemplaryembodiments, a post 211 may only partially fill or occupy an aperture131. For example, a post 211 may be configured as a hollow cylinder andthus occupy all edges of a corresponding circular aperture 131, whileleaving a smaller cylindrical area of aperture 131 unoccupied. Moreover,a post 211 may be configured as a cylinder having a notch out of theside thereof, such that post 211 occupies most of a circular aperture131 while leaving a small void along one edge portion of that aperture131. In this manner, flow of vapor and/or working fluid 115 in eitherdirection through aperture 131 is facilitated, for example in order tofacilitate a more constant vapor pressure (and thus, a more constantsaturation temperature point) in all relevant locations in thermalmanagement system 100.

In some exemplary embodiments, a post 211 is configured to be generallyflush with both the edges of a corresponding aperture 131 and the edgesof one or more associated battery cells 112. For example, a post 211 mayhave a generally cylindrical form factor for a first portion of post 211(i.e., a portion intended for insertion into an aperture 131), and, fora second portion of post 211, a form factor of a pseudotriangle havingtruncated ends (i.e., a form factor intended to fit in the space betweenclosely packed cylindrical battery cells 112, for example as depicted inFIG. 2C). In these embodiments, the length of the first portion of post211 may govern the distance to which post 211 is insertable throughcorresponding aperture 131.

In various exemplary embodiments, posts 211 may extend through apertures131 such that the bottom of posts 211 contact the far side ofcondensation chamber 140 (i.e., a portion of each post 211 traversesfrom one side of condensation chamber 140 all the way to the opposingside). In this manner, posts 211 may absorb working fluid 115 pooled atany depth in condensation chamber 140. In other exemplary embodiments,posts 211 may extend through apertures 131 such that the bottom of posts211 reach only partway into condensation chamber 140, instead of fullytraversing condensation chamber 140. In these configurations, whencondensation chamber 140 is disposed horizontally, a minimum pool depthof working fluid 115 will be present in condensation chamber 140 beforethe pool of working fluid 115 contacts the bottom of posts 211. Thisconfiguration facilitates an even distribution of working fluid 115 incondensation chamber 140, as working fluid 115 is permitted to flowlaterally in all directions. In contrast, in some embodiments whereposts 211 extend all the way to the opposing wall of condensationchamber 140, posts 211 may absorb and transport working fluid 115vertically at a quicker rate than working fluid 115 can flow laterallywithin condensation chamber 140, thus leading to “dry” or “drier” posts211 (i.e., posts 211 having reduced access to working fluid 115;typically, such posts may arise within the central area of an array ofposts 211 in thermal management system 100).

Moreover, in some exemplary embodiments, a combination may be utilizedwherein some posts 211 extend only partially into condensation chamber140, and other posts 211 fully traverse condensation chamber 140. Forexample, alternating posts 211 may be interleaved, such as in acheckerboard pattern. In another example, every third post 211 in a lineof posts 211 may fully traverse condensation chamber 140. In yet anotherexample, every third post 211 in a line of posts 211 may extend onlypartway into condensation chamber 140. In yet other examples, posts 211fully traversing condensation chamber 140 and posts 211 extending onlypartway into condensation chamber 140 may be arranged in stripes,spirals, concentric geometric shapes, and/or the like. In these combinedapproaches, unimpeded lateral flow of working fluid 115 withincondensation chamber 140 is provided, while still ensuring a sufficientrate of transport of working fluid 115 upwards into vapor chamber 110.Moreover, in thermal management system 100, any suitable arrangement ofposts 211 fully traversing condensation chamber 140 and posts 211extending only partway into condensation chamber 140 may be utilized.

With reference now to FIGS. 11A and 11B, in some exemplary embodiments,in thermal management system 100, certain apertures 131 are notpartially or fully filled with a post 211, but are instead left asunobstructed passageways or paths linking vapor chamber 110 andcondensation chamber 140. In one example, alternating apertures 131 maybe left empty, for example in a checkerboard pattern. In anotherexample, every third aperture 131 in a line of apertures 131 may be leftempty. In yet another example, cold plate 130 may be configured with anarray of apertures 131 such that empty apertures 131 and apertures 131filled with posts 211 form concentric rings or outlines generallycentered in the middle of cold plate 130. In still another example,empty apertures 131 may be arranged in alternating rows or stripes withapertures 131 filled with posts 211. Moreover, the selection ofapertures 131 to be left empty, and the selection of apertures 131 to beoccupied by posts 211, may be any suitable pattern, for example in orderto achieve a desired circulation of vapor and working fluid 115 withinthermal management system 100.

It will be appreciated that, in various exemplary embodiments, thermalmanagement system 100 may utilize both unobstructed (and/or partiallyobstructed) apertures 131 and capillary tubes 114. In some exemplaryembodiments, thermal management system 100 may utilize only unobstructed(and/or partially obstructed) apertures 131, and may be configuredabsent any capillary tubes 114. In yet other exemplary embodiments,thermal management system 100 may utilize capillary tubes 114, and maybe configured absent any unobstructed (and/or partially obstructed)apertures 131.

In various exemplary embodiments, in thermal management system 100,capillary tubes 114 may be positioned, shaped, and/or otherwiseconfigured based at least in part on a direction and/or path of coolant(more generally, thermal fluid) flow in an associated cold plate 130.For example, during operation of heat pump 150, thermal fluid is pumpedacross cold plate 130, for example in a serpentine-like path. Whenthermal management system 100 is operative in a cooling mode, thethermal fluid gains heat as it traverses cold plate 130. Accordingly,the thermal fluid is at a higher temperature when it exits contact withcold plate 130 as compared to when it begins contact with cold plate130. Thus, in some exemplary embodiments, thermal management system 100is configured with one or more capillary tubes 114 having return endsdisposed generally on a common side of vapor chamber 110 as the portionof cold plate 130 where thermal fluid exits cold plate 130 (i.e., whenthermal management system 100 is operative in a cooling mode, theportion that is the “hottest” portion of cold plate 130). In thismanner, an increased supply of working fluid 115 may be supplied to anarea in vapor chamber 110 where direct cooling of battery cells 112 bycold plate 130 is at a minimum, thus affording increased cooling tobattery cells 112 in that area via phase change of working fluid 115.Additionally, in some exemplary embodiments, the dimensions, lengths,paths, number of intake ends, number of return ends, and/or othercharacteristics of capillary tubes 114 in thermal management system 100may be selected based on characteristics of thermal fluid flow in coldplate 130. For example, a particular capillary tube 114 may traverseand/or travel along a portion of cold plate 130 in a direction generallyparallel to thermal fluid flow in cold plate 130. Another particularcapillary tube 114 may traverse and/or travel along a portion of coldplate 130 in a direction generally counter or opposite to the directionof thermal fluid flow in cold plate 130. Stated generally, in thermalmanagement system 100, capillary tubes 114 may be utilized to moreclosely approximate isothermal conditions within vapor chamber 110and/or provide approximately equal cooling capacity for each batterycell 112 in thermal management system 100 (for example, cooling capacityfor battery cells 112 varying by no more than 10% from highest to lowestcapacity).

Turning now to FIGS. 12A through 12C, in various exemplary embodiments,thermal management system 100 may utilize an array of posts 211 wherethe length, thickness, material, or other characteristics of aparticular post 211 varies depending at least in part on the position ofthat particular post 211 in the array. For example, with reference nowto FIG. 12A, which shows a view along a length of a thermal managementsystem 100, it can be seen that a particular post 211-A disposed nearthe outer edge of the array of posts 211 may be configured with a lowerheight than another post 211-B disposed near the center of the array ofposts 211. Posts 211 nearer the center of the array may be configuredwith a greater height, for example in order to provide increased coolingcapacity to associated battery cells 112. Similarly, with reference toFIG. 12B, which shows a view along a width of thermal management system100, it can be seen that post 211-C is shorter than post 211-D, which inturn is shorter than post 211-E. With reference to FIG. 12C, which showsa perspective view of the array illustrated in FIGS. 12A and 12B, it canbe seen that variations in height of posts 211 may be applied acrossboth length and width of thermal management system 100. In this manner,posts 211 in thermal management system 100 may be configured to provideappropriate cooling capacity to associated battery cells 112,particularly in areas located generally in the center of thermalmanagement system 100 where heat loads tend to be greatest.

The heights of posts 211 may vary in a linear manner, a curved manner, astepwise manner, or any other suitable manner. For example, the heightsof posts 211 may have a first value in a first ring-shaped area disposedgenerally along the outer edge of the array of posts 211, and a second,higher value in the inner area enclosed by the first ring-shaped area.In another example, moving along a length of thermal management system100, posts 211 may taper up in height, reach a maximum, and at somepoint thereafter taper back down, resulting in a somewhat triangularand/or trapezoidal cross-section (i.e., as illustrated in FIGS. 12A and12B).

It will be appreciated that the exemplary embodiments disclosed in FIGS.8A through 12B are compatible with, and may be used in any suitablecombination with, the various system configurations and orientationsdisclosed in connection with the discussion of FIGS. 1A through 1E.

In an exemplary embodiment, a vapor chamber for transferring heatbetween the vapor chamber and a heat pump comprises an outer housing, awicking material contained within the outer housing, and a working fluidat least partially absorbed by the wicking material. The vapor chamberis configured with a plurality of apertures to accept portions of aplurality of battery cells therein. The vapor chamber facilitates closepacking of the plurality of battery cells. The battery cells may bedisposed less than 1 mm from one another. The vapor chamber is operativeto cool the battery cells, regardless of the orientation of the vaporchamber with respect to gravity. A battery cell in the plurality ofbattery cells has a first end and a second end distal from the firstend, the first end and second end having a length therebetween. Thewicking material may be in contact with 10% to 50% of the length of thebattery cell. The wicking material may be in contact with the batterycell starting at the first end and extending along 5% to 50% of thelength of the battery cell. The wicking material may vary in thicknessalong the length of the battery cell. The wicking material may vary inporosity along the length of the battery cell. The wicking material maybe configured as a contact ring having a honeycomb shape. The wickingmaterial may be configured with a parallel weave configuration. Thewicking material may be configured with a serial weave configuration.The battery cells may be conductively coupled to a cold plate forming anedge of the vapor chamber. The vapor chamber may be coupled to a heatpump via a cold plate.

In another exemplary embodiment, a method for cooling a battery packcomprising a plurality of battery cells comprises identifying, in thebattery pack, a set of battery cells that are edge cells. The methodfurther comprises identifying, in the battery pack, a set of batterycells that are inner cells. The method further comprises identifying, inthe battery pack, a set of battery cells that are center cells. Themethod further comprises coupling the plurality of battery cells to avapor chamber, disposing a working fluid within the vapor chamber, anddisposing a wicking material in the vapor chamber. The method furthercomprises coupling, to the edge cells, a first amount of the wickingmaterial, coupling, to the inner cells, a second amount of the wickingmaterial different than the first amount, and coupling, to the centercells, a third amount of the wicking material different than the firstamount or the second amount. The method may further compriseidentifying, in the battery pack, a set of battery cells that are entrycells, and identifying, in the battery pack, a set of battery cells thatare exit cells. The method may further comprise configuring the wickingmaterial such that the amount of wicking material coupled to the entrycells differs from the amount of wicking material coupled to the exitcells. The method may further comprise coupling, to the edge cells, afirst amount of the wicking material having a first wickingcharacteristic, coupling, to the inner cells, a second amount of thewicking material having a second wicking characteristic different fromthe first wicking characteristic, and coupling, to the center cells, athird amount of the wicking material having a third wickingcharacteristic different from the first wicking characteristic or thesecond wicking characteristic.

In an exemplary embodiment, a method for thermal regulation of a batterypack comprises disposing a plurality of battery cells at least partiallywithin a vapor chamber, the plurality of battery cells forming a batterypack, and the vapor chamber comprising a housing, a wicking material,and a working fluid; and contacting each of the plurality of batterycells with at least a portion of the wicking material. During chargingor discharging of the battery pack, the working fluid changes phasewithin the vapor chamber in order to carry heat away from the batterycells. The method may further comprise coupling a heat pump to the vaporchamber via a cold plate. The vapor chamber may be operative to carryheat away from the battery cells without regard to the orientation ofthe vapor chamber with respect to gravity. The method may furthercomprise monitoring, during charging or discharging of the battery pack,at least one of temperature or pressure within the vapor chamber; andresponsive to the monitoring, adding or removing an amount of workingfluid to the vapor chamber.

In another exemplary embodiment, a thermal management system for anindividual battery cell comprises a coldwell comprising a housing, awicking material, and a working fluid; and a battery cell disposed atleast partially within the coldwell such that the bottom of the batterycell contacts the wicking material. The interface between the batterycell and the housing is sealed to retain the working fluid within thehousing, and the working fluid changes phase within the coldwell inorder to carry heat away from the battery cell.

In another exemplary embodiment, a thermal management system for abattery pack comprises a vapor chamber comprising a housing, a wickingmaterial, and a working fluid; a cold plate coupling the vapor chamberto a heat pump; the battery pack comprising a plurality of batterycells, each of the plurality of battery cells disposed at leastpartially within the vapor chamber; a condensation chamber coupled tothe cold plate; and a capillary tube linking the vapor chamber and thecondensation chamber. Each battery cell contacts a portion of thewicking material, and the working fluid changes phase within the vaporchamber in order to carry heat away from the battery cells.

The wicking material may be configured as a set of posts disposedbetween the battery cells. The cold plate may be disposed between thevapor chamber and the condensation chamber. The cold plate may beconfigured with a plurality of apertures therethrough to link the vaporchamber and the condensation chamber. A first portion of the pluralityof apertures may be occupied by the wicking material, and a secondportion of the plurality of apertures may not be occupied by the wickingmaterial. A portion of the wicking material may comprise a post, and thepost passes through an aperture and fully traverses the condensationchamber. A portion of the wicking material may comprise a post, and thepost partially occupies one of the plurality of apertures. The capillarytube may be configured with a plurality of intake ends leading to acommon portion of the capillary tube. The capillary tube may have anintake end on a first side of the vapor chamber and a return end on anopposing side of the vapor chamber. The capillary tube may be configuredwith an inner diameter of between 1 mm and 12 mm. Evaporation of theworking fluid from the wicking material may cause vapor to flow into thecapillary tube. The wicking material may be configured as an array ofposts, and the array of posts vary in height from one another. The arrayof posts may vary in height in a stepwise manner as viewed along alength of the array of posts.

While the principles of this disclosure have been shown in variousembodiments, many modifications of structure, arrangements, proportions,the elements, materials and components, used in practice, which areparticularly adapted for a specific environment and operatingrequirements may be used without departing from the principles and scopeof this disclosure. These and other changes or modifications areintended to be included within the scope of the present disclosure andmay be expressed in the following claims.

The present disclosure has been described with reference to variousembodiments. However, one of ordinary skill in the art appreciates thatvarious modifications and changes can be made without departing from thescope of the present disclosure. Accordingly, the specification is to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of thepresent disclosure. Likewise, benefits, other advantages, and solutionsto problems have been described above with regard to variousembodiments. However, benefits, advantages, solutions to problems, andany element(s) that may cause any benefit, advantage, or solution tooccur or become more pronounced are not to be construed as a critical,required, or essential feature or element of any or all the claims.

As used herein, the terms “comprises,” “comprising,” or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchthat a process, method, article, or apparatus that comprises a list ofelements does not include only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Also, as used herein, the terms “coupled,”“coupling,” or any other variation thereof, are intended to cover aphysical connection, an electrical connection, a magnetic connection, anoptical connection, a communicative connection, a functional connection,a thermal connection, and/or any other connection. When language similarto “at least one of A, B, or C” or “at least one of A, B, and C” is usedin the specification or claims, the phrase is intended to mean any ofthe following: (1) at least one of A; (2) at least one of B; (3) atleast one of C; (4) at least one of A and at least one of B; (5) atleast one of B and at least one of C; (6) at least one of A and at leastone of C; or (7) at least one of A, at least one of B, and at least oneof C.

What is claimed is:
 1. A thermal management system, including: a vaporchamber comprising a housing and a working fluid; a battery packcomprising a plurality of battery cells, each of the plurality ofbattery cells disposed partially within the vapor chamber, wherein theworking fluid changes phase within the vapor chamber in order to carryheat away from the plurality of battery cells; a heat pump coupled tothe vapor chamber via a cold plate; a condensation chamber coupled tothe cold plate; and a capillary tube having an intake end at a firstlocation within the vapor chamber and a return end at a second,different location within the vapor chamber, wherein the capillary tubepasses at least partially through the condensation chamber.
 2. Thesystem of claim 1, wherein electrical terminals of at least one batterycell of the plurality of battery cells are outside the vapor chamber. 3.The system of claim 1, wherein the vapor chamber is configured with oneor more of an orifice or a seal configured to partially receive at leastone of the plurality of battery cells while retaining the working fluidwithin the vapor chamber.
 4. The system of claim 1, the vapor chamberhaving a top and a bottom, wherein the vapor chamber is oriented suchthat gravity pulls the working fluid down along a battery cell wall. 5.The system of claim 4, wherein the working fluid evaporates adjacent tothe bottom of the vapor chamber and condenses on a plate located at thetop of the vapor chamber.
 6. The system of claim 1, wherein the thermalmanagement system is operative to provide a level of thermal transfer toeach battery cell that is at least 500 watts per meter-Kelvin (W/mK) andup to 2000 W/mK.
 7. An electric vehicle comprising: a thermal managementsystem, including: a vapor chamber comprising a housing and a workingfluid; and a battery pack comprising a plurality of battery cells, eachof the plurality of battery cells disposed partially within the vaporchamber, wherein the working fluid changes phase within the vaporchamber in order to carry heat away from the plurality of battery cells;an electric motor coupled to the battery pack; a heat pump coupled tothe vapor chamber via a cold plate; a condensation chamber coupled tothe cold plate; and a capillary tube having an intake end at a firstlocation within the vapor chamber and a return end at a second,different location within the vapor chamber, wherein the capillary tubepasses at least partially through the condensation chamber.
 8. Theelectric vehicle of claim 7, wherein electrical terminals of at leastone battery cell of the plurality of battery cells are outside the vaporchamber.
 9. The electric vehicle of claim 7, wherein the vapor chamberis configured with one or more of an orifice or a seal configured topartially receive the at least one of the plurality of battery cellswhile retaining the working fluid within the vapor chamber.
 10. Theelectric vehicle of claim 7, the vapor chamber having a top and abottom, wherein the vapor chamber is oriented such that gravity pullsthe working fluid down along a battery cell wall.
 11. The electricvehicle of claim 10, wherein the working fluid evaporates adjacent tothe bottom of the vapor chamber and condenses on a plate located at thetop of the vapor chamber.
 12. The electric vehicle of claim 7, whereinthe thermal management system is operative to provide a level of thermaltransfer to each battery cell that is at least 500 watts permeter-Kelvin (W/mK) and up to 2000 W/mK.